Many infectious diseases have been overcome by development of various bactericides/disinfectants, antibiotics, and synthetic antibacterial agents, and the average life span of human beings has been considerably extended. On the other hand, however, many bacteria resistant to these drugs appear and, at the same time, in elderly people, so-called opportunistic infection with bacteria which are usually weak in their infectious power has been increased due to a cause such as reduction in immunity, and increase in hospital infection and population infection in other facilities has become a great social problem. Especially in recent years, infectious diseases which cannot be treated by conventional drugs, including those caused by methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) or, nowadays those caused by vancomycin-resistant MRSA, multiple drug-resistant Pseudomonas aeruginosa, pneumococcus and Serratia bacteria, have increased rapidly, and development of effective methods of preventing or treating such diseases is now keenly desired.
Since the discovery of 4,6-diamino-1-(p-chlorophenyl)-1,2-dihydro-2,2-dimethyl-s-triazine (Cycloguanil) which is an active metabolite of an anti-malaria agent Proguanil fifty several years ago (Journal of Pharmacology 1947, Vol. 2, p. 161-168; British H. C. Carrington et al., Nature 1951, Vol. 168, p. 1080), various patent applications or study reports have been made.
For example, E. J. Modest et al., Journal of the American Chemical Society 1952, Vol. 74, p. 855-856 describes anti-vitamin activity and anti-malaria activity of 4,6-diamino-2,2-dimethyl-s-triazine derivatives. E. J. Modest et al., Journal of Organic Chemistry 1956, Vol. 21, p. 1-13, p. 14-20 describes 4,6-diamino-1,2-dihydro-2,2-dimethyl-1-phenyl-s-triazines regarding anti-vitamin, anti-malaria, anti-cancer and anti-coccidium activities. U.S. Pat. No. 5,565,451 describes the use of 1-(3-phenylpropyl)-2,4-diamino-6,6-dimethyl-1,6-dihydro-1,3,5-triazines as an insecticide. EP No. 0504290 describes that 4,6-diamino-1,2-dihydro-1-phenyl-s-triazines have an action of inhibiting growth of Pneumocystic carinii. WO 01/53276 describes the use of 1-p-chlorophenyl-4,6-diamino-1,2-dihydro-1,3,5-triazine and the like as an anthelmintic (anti-malaria agent etc.). However, the aforementioned known references do not refer to antibacterial activity at all.
U.S. Pat. No. 3,682,912 describes 4,6-diamino-1,2-dihydro-1,3,5-triazine derivatives as a compound having antibacterial activity in addition to anti-malaria activity, and U.S. Pat. No. 3,723,429 describes 4,6-diamino-1,2-dihydro-1,3,5-triazine derivatives as an anti-malaria/antibacterial active compound. However, since compounds described in these known references have all a substituent at position 1 of the 1,2-dihydro-1,3,5-triazine ring using —O— as an intervening group, they are different compounds from those of the present invention, and no data of antibacterial activity are described therein.
U.S. Pat. No. 3,287,365 describes a compound represented by the following formula (4) having herbicidal activity in Working Example 5, but antibacterial activity thereof is not described at all.

U.S. Pat. No. 3,287,366 describes a compound represented by the following formula (5) having herbicidal activity in Working Example 3, but nothing is known about antibacterial activity thereof.

Andre Rosowsky et al., Antimicrobial Agents and Chemotherapy 1995, Vol. 39, p. 79-86 describes a compound represented by the following formula (6) as a dehydrofolate reductase inhibitor (anthelmintic (anti-malaria)). However, the aforementioned known reference does not describe antibacterial activity of the same compound at all.
